Data carrier with an optically variable element

ABSTRACT

The invention relates to a data carrier, in particular bank note, paper of value, identity card or the like, having a security element disposed on the surface thereof. The data carrier is provided in at least one partial area with a background layer containing at least one authenticity feature. The optically variable element is applied to this background layer such that it overlaps the latter at least partly but does not completely cover it.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a data carrier, in particular a bank note,paper of value, identity card or the like, having a security elementdisposed on the surface thereof.

2. Background of the Invention

For protecting data carriers, in particular security documents,manufacturers provide these documents with additional security elementsintended to authenticate them, on one hand, and to serve as protectionfrom unauthorized reproduction of the data carrier, on the other hand.Along with a number of elements which have been produced by separateprinting or other production processes, the use of optically variableelements which are applied to such data carriers have become widespread.

For detecting the authenticity of a document having a security elementin the form of a reflection hologram consisting of an embossed layer oflacquer and a reflecting metal layer, it has been proposed for examplein WO 94/11203 to use an adhesive layer with a fluorescent substance forapplying the optical security element to the document. For detecting theauthenticity of the document this fluorescent substance can betransferred to the document together with the optical security feature.However the fluorescent substance is only visible if openings areprovided in the metal layer of the element so that the fluorescentsubstance is visible through the openings. Alternatively it has beenproposed in WO 94/11203 that the document material be transparent sothat the adhesive layer bearing the fluorescent substance is visiblefrom the side facing away from the optical security element.

A disadvantage of the fluorescent adhesive known from WO 94/11203 isthat it can only be applied in documents or optical security elementswhich fulfill special boundary conditions suitable for the adhesive.Specifically, the document material must either be transparent or theoptical security element to be used must provide a view of thesubjacent, fluorescent adhesive layer at least in partial areas. Anotherdisadvantage is that the element could be detached and glued to afalsified document without this abuse being recognizable, since part ofthe fluorescent adhesive layer would still adhere to the element afterits detachment and thus still provide a qualitatively correctauthenticity signal, although it is quantitatively too small due to alower fluorescence intensity. When authenticity elements are quicklytested, only the qualitative properties are usually evaluated, such asthe presence of fluorescence or its wavelength, so that insufficientintensity of the signal does not enter into the detection of whether ornot a document is authentic.

The problem to be solved is to provide a document with a securityelement wherein the security element on the document can be protectedeffectively without the document or security element having to meetspecial requirements of the type described.

BRIEF SUMMARY OF THE INVENTION

According to the invention a security element is protected by specialpretreatment of the document material in the area of the element to beapplied. This establishes a relation between document and element whichpermits attempted forgery to be prevented or at least easily discovered.In the simplest embodiment the pretreatment consists in applying abackground layer provided with visually and/or machine detectablefeature substances, the element being applied to the background layersuch that the background layer is not covered by the element at least ina partial area and is thus freely accessible from outside. The featuresubstances can thus be detected unhindered in the uncovered area of thebackground layer with no need for special measures in the element layerstructure or special document materials.

Furthermore the feature substances can provide information about theauthenticity of the document material since they are not bound to theelement and the layer structure thereof. If a luminescent substance isadmixed to the background layer for example, a forgery consisting ofcopied document material and an authentic element can be ascertainedvery easily since the fluorescent substances cannot be rendered by acolor copier, or at least not true to the original. This makes itpossible not only to protect documents better from forgery orfalsification but also to detect the originality of products and thusincrease product assurance.

Machine testing of the element is likewise facilitated by the inventivecombination of pretreating the document material and applying thesecurity element to the pretreated area in overlapping fashion. Via thebackground layer provided with a machine detectable feature one caneasily localize the area in which the element should be disposed. If thefeature is additionally a feature which is shielded by the element, onecan at the same time determine from the superficial extension of thefeature substance whether the element is completely lacking or might behighly damaged.

In this way one can determine for example the fitness for circulation ofa bank note provided with a hologram. If the background layer containse.g. a fluorescent substance whose excitation and emission are preventedby the metal layer located within the hologram layer structure, theextension of the fluorescent surface increases when parts of the metallayer and thus the element layer structure are lacking. The fluorescentradiation also penetrates through cracks in the metal layer so that thefluorescence occurring in the element area is a measure of the conditionof the element and the optical effect thereof. This can also be used todefine a decision criterion for the bank note's fitness for circulation.

If the document material consists of paper with high surface roughnesssuch as bank note paper, the element is preferably underlaid all overwith the background layer, the superficial extension of the backgroundlayer being greater at least in one direction than the opticallyvariable element applied to this surface. This not only producesadditional protection from forgery for the document, but simultaneouslyavoids impairment of the optical impression of the element due to thesurface roughness. As already described in EP 0 440 045 A2, the adverseeffects of the document material surface quality can be avoided bymechanical smoothing in certain areas or by applying a smoothingbackground layer.

According to a further embodiment the background layer can also beapplied to one or more layers already present on the document, e.g.primer layers. It can furthermore consist of different zones containingdifferent feature substances. These zones can also overlap so that e.g.areas with mixed luminescences arise if different luminescent substancesare used. The background layer can be doctored on, sprayed on withnozzles or printed with any printing process.

The added feature substances are preferably luminescent pigments. Theyhave the advantage that they cannot be rendered by a copier, or not trueto the original, and are therefore a very effective means of preventingforgery using color copying machines. Simultaneously the luminescentpigments can be easily detected with standard detectors and thus provethe authenticity of a document. If the emission wavelength is in thevisible spectral region, the luminescent pigments can also serve as avisual authenticity feature which can be detected quickly and easily byillumination with a suitable excitation source.

However it is also possible to provide the background layer with otherauthenticity features. One can use in particular metallic pigments, weakpastel tones or pigments giving the primer layer a color which standsout only slightly from the color of the paper. One can further usemagnetic, electrically conductive, radioactive substances or onesabsorbent in the visible or invisible spectral region as well asinterference layer pigments or liquid-crystal pigments.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments and advantages of the invention will be explained inthe following with reference to the figures, the representation notbeing true to scale for clarity's sake.

FIG. 1 shows a data carrier according to the invention,

FIG. 2 shows an enlarged detail of the inventive data carrier in thearea of the optically variable element,

FIG. 3 shows a further embodiment of the inventive data carrier in anenlarged detail in the area of the optically variable element,

FIG. 4 shows the detail of an inventive data carrier in the area of anapplied optically variable element,

FIG. 5 shows a further embodiment of the inventive data carrier in anenlarged detail in the area of the optically variable element,

FIG. 6 shows a further embodiment of the inventive data carrier in thearea of the element in cross section.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows a data carrier in the form of bank note 1 having anoptically variable stripe 2 applied as an endless element to the banknote. The data carrier material used can be paper, a fabric of naturaland/or synthetic fibers or a plastic film. Optically variable stripe 2has been applied to a surface area of the bank note which is formed inthe present case by background layer 3 located all over under theoptically variable element. This area cannot be rendered with a copiersince background layer 3, which preferably consists of a layer oflacquer, has had luminescent substances mixed thereinto which cannot betransferred to the copy with the help of copying technology and are thuslacking in the copy. When the authenticity of the bank note is checked,for example with the help of a UV lamp or an authenticity sensor whichcan recognize the incorporated luminescent substance, the absence ofthis feature can be immediately recognized even if an attempt was madeto reproduce optically variable element 2 or transfer authentic element2 to a copy of bank note 1.

Instead of adding luminescent substances which can emit in the visibleand/or invisible spectral region, one can also enrich the backgroundlayer 3 with other substances which prevent true reproduction of thebank note with the help of a copier. These include for exampleinfrared-emitting or infrared-absorbent pigments. In addition one canuse magnetic or conductive substances. It is especially suitable to usetheremochromic or photochromic substances and substances forradioactively labeling the primer layer.

Although the background layer can basically be applied by all knownmethods, it is especially advantageous to apply it by screen printing,flexography or halftone photogravure. With this technology one canfirstly adapt the contours of background layer 3 very exactly to thedesired requirements. Furthermore one can print the background layer insuch a way that it produces an additional optical effect.

FIG. 2 shows an example of this, indicating only a detail of inventivedata carrier 1. Optically variable element 2 covers an area of datacarrier 1 which is covered all over with background layer 3. Thequantity of background layer material applied per surface unit decreasestoward edges 4 of background layer 3 extending away from opticallyvariable element 2, resulting in a diminishing-edge progressive pattern.This can be effected quite simply by screen printing, the progressionbeing designed as a dot screen progression, line screen progression orpattern progression in which the number of patterns printed per surfaceunit decreases clearly toward the edge. The background layer coveringcan decrease continuously or in steps. Alternatively it is also possibleto keep the quantity of background layer material constant over theentire area and vary only the concentration of the feature substance.

FIG. 3 shows a further embodiment of inventive data carrier 1 in anenlarged detail in the area of optically variable element 2. Opticallyvariable element 2 is again a holographic stripe containing information7 in the form of a diffractive relief structure which is visible from atleast one viewing angle. In the present example information 7 consistsof the letters "GD". As in the example of FIG. 4, the holographic stripewas applied to background layer 3 which has a diminishing-edgestructure. However background layer 3 was printed such that information7 present in the holographic stripe appears again in the backgroundlayer outside holographic stripe 2.

The size and design of information 6 is freely selectable. In theexample shown in FIG. 3 the letters "GD" were repeated in a smallerform, but the arrangement and form of the characters is random and canbe adapted to the particular needs. Characters 6 can be incorporated inbackground layer 3 by a positive or negative method. In the negativemethod background layer 3 is left out in the area of characters 6 sothat the particular physical property of background layer 3 is notrecognizable at this place. The color of background layer 3 preferablydoes not differ substantially from the color of the data carriersurface. If luminescent substances are thus mixed into background layer3, this only becomes noticeable upon viewing of layer 3 under anexciting light source by the lack of otherwise present luminescence inthe area of characters 6 so that characters 6 are readily recognizableagainst a luminescent background.

For positive representation of characters 6 one can apply an additionalprint to the background layer. The print can involve for example asecond luminescent color differing from the color of the background.However other combinations are also possible in which the print is donefor example with magnetic or other, abovementioned, suitable pigments oradditives. Characters 6 can likewise be printed with a transparent oropaque ink covering the subjacent fluorescent substance at least partly.This results in manifold possibilities of combination for the personskilled in the art in designing the background to which the opticallyvariable element is applied and furthermore providing it with a furtherprint for security purposes. Positive representation of characters 6 canalso be done differently. It is thus conceivable to leave out thebackground layer in an area of any desired shape, e.g. in the form of arectangle, and represent characters 6 in this free area either with thesame material as surrounding background layer 3 or with a differentmaterial.

A particular advantage of the embodiment shown in FIG. 3 is that thistechnique can provide a correspondence in information between datacarrier 1 and optically variable element 2 applied to data carrier 1,thereby permitting identification of optically variable element 2 withdata carrier 1.

For this purpose one can e.g. also conform information 7 in opticallyvariable element 2 with further, corresponding information 5 applied todata carrier 1 at basically any place. Especially advantageous examplesfor bank notes are denomination, issuing office or other graphicelements coordinated with a certain value of a note. One can alsoprovide triple rendition of information by repeating information 5applied elsewhere to the document, e.g. the denomination, in backgroundlayer 3 and in the element (information 6,7).

According to a further variant one can also establish a correspondencebetween information visible from all viewing angles provided in themetal layer of optically variable element 2 and additional information 6in background layer 3. Information 7 present in the metal layer can beproduced e.g. by demetalizing, the information being represented as gapsor else as metallic characters in a demetalized zone. This informationcan be repeated in background layer 3.

Alternatively one can execute incorporated pieces of information 6 and 7or information 6 and information 5 on the data carrier such that theysupplement each other to form total information. In the latterembodiment one can include information 7 present in element 2. For thispurpose the information present in element 2 can repeat or supplementone or more of the pieces of information present in the metal layer, thebackground layer or on the document, or the total information. In theseembodiments the register between element 2 and background layer 3 orbetween information 6 in the background layer and information 5 on thedata carrier must meet high requirements which are practicallyimpossible for a counterfeiter to fulfill.

Information 6 applied additionally to, or left out of, background layer3 can also be executed so as to be machine-readable and optionally alsohave a correspondence with optically variable element 2 applied.Information 6 can thus be applied, not as letters GD shown in FIG. 3,but in the form of binary codings or other machine-readable characters.For example the bank note denomination also present in the opticallyvariable element could be applied as machine-readable information 6. Oneagain has all the above-described possibilities for applying theadditional information. It is of particular interest to use a magneticcoding which can be executed for example as a visible or invisible barcode.

Along with the hitherto described optically variable elements which areusually transferred to the document in the form of endless stripes bytransfer technology, it is also possible to apply an optically variableelement as a so-called single element. Such elements are located at asuitable place on the surface of the data carrier without connecting twoedges of the data carrier. There are no restrictions on their shape. Inparticular these elements can be constituted by basic geometricstructures such as circles, rectangles, polygons, or combinationsthereof. The shape of the background layer is preferably coordinatedwith the shape of the element. FIG. 4 shows an example where in an areaof data carrier 1, which is again shown enlarged, optically variablesingle element 8 is applied in partial area 3 of the data carrier whichagain has the desired properties. Depending on the shape and motif ofoptically variable element 8 the subjacent area can be adapted in shapeand size according to the particular requirements.

The optically variable element can also be produced directly on thedocument. In the case of a hologram, for example, this can be done bybringing a lacquer-coated embossing roll in contact with the documentmaterial and curing the lacquer during contact. One then provides thislacquer with a metal layer. However the metal layer can also be producedon the embossing roll and transferred together with the layer of lacquer(EP 0 563 992 A2). The edges of the area which face away from theoptically variable element can have the same form as the edges of theoptically variable element or be designed differently according to theparticular requirements. Furthermore the edge design of element 2 or 8can be executed so as to produce additional, difficultly imitableeffects. For this purpose the edges can be executed for example as teeth9 or patterns 10 covering area 3 only partly, as shown in a few examplesin FIG. 5.

FIG. 6 shows an embodiment in which background layer 3 consists ofseveral zones 11, 12, 13. Zones 11, 12, 13 differ primarily with regardto their physical properties. Different luminescent substances can thusexist in different zones 11, 12, 13 so that for example zone 13fluoresces when excited in the red spectral region and zone 11phosphoresces in the green. When the excitation is switched off thegreen emission of zone 11 persists for a certain time in this case,while the emission of the fluorescent substance in zone 13 ends when theexcitation is switched off. Middle zone 12 can contain a furtherluminescent substance or another feature substance which becomesdetectable for example only when element 2 has a certain degree ofwornness due to breaks therein. Zone 12 could also be free of anyfeature substance if this appears suitable. Different zones 11, 12, 13could likewise overlap at least partly to produce mixed effects.

Also one can dispose further layers under background layer 3. It is forexample conceivable to apply a primer layer not pigmented with featuresubstances to the document for smoothing the surface, and the pigmentedbackground layer only in a small partial area so that the element thenapplied overlaps the background layer but is not disposed completelythereon.

In the above-described examples it is also unnecessary for thebackground layer to be disposed under the element all over. It need onlybe freely accessible in at least one place.

Along with holograms one can use all other optically variable elementswhich convey different optical impressions from at least two differentviewing angles. It is thus also within the scope of the invention to useoptically variable inks, optically variable thin-layer films, cinegrams,pixelgrams, stereograms and other variants of holograms as well asvolume holograms, iriodine prints or paliochromes as well as metal filmsor other metallic coatings with or without embossed structures. One canlikewise use mere embossings of the substrate as optically variableelements which lead to an optically variable effect. The use of bronzeinks or polymeric liquid-crystal inks is also within the range of theinventive possibilities.

Furthermore one can apply other security elements, i.e. ones which arenot optically variable, to an inventive data carrier and protect them bythe inventive method.

Although the invention has been described substantially in terms ofprotecting data carriers such as security documents, the inventiveoptically variable security elements are also suitable for protectingproducts, in particular products of high value. The inventive securityelement can be applied for example to merchandise labels, CDs or otherarticles of sale whose originality can be detected using the inventivesecurity element. Such products are thus also to be regarded as datacarriers in the sense of the invention.

We claim:
 1. A data carrier with a surface, the surface being providedat least in a partial area with a background layer comprising at leastone testable substance indicating authenticity of the data carrier,wherein the surface of the data carrier is provided with a securityelement and wherein the security element at least partially overlaps thebackground layer such that the background layer is not completelycovered by the security element and the substance is still testable inthe uncovered area of the background layer.
 2. The data carrier of claim1, wherein the security element is an optically variable element showingdifferent optical images when viewed from at least two different viewingangles.
 3. The data carrier of claim 1, wherein the security elemententirely overlaps the background layer.
 4. The data carrier of claim 1,wherein the background layer comprises at least two layers, each layercomprising a different testable substance.
 5. The data carrier of claim4, wherein the layers are disposed side by side.
 6. The data carrier ofclaim 4, wherein the layers are disposed one over the other.
 7. The datacarrier of claim 4, wherein the layers are disposed partly overlappingeach other.
 8. The data carrier of claim 1, wherein at least oneadditional layer is disposed below the background layer.
 9. The datacarrier of claim 1, wherein the testable substance is selected from thegroup consisting of luminescent, metallic, magnetic, electricallyconductive substances and optically variable pigments.
 10. The datacarrier of claim 1, wherein the quantity of the background layer persurface unit decreases with the distance from the security element. 11.The data carrier of claim 1, wherein the background layer comprises apredetermined concentration per surface unit of the testable substanceand wherein the concentration per surface unit decreases as the distanceof the background layer from the security element increases.
 12. Thedata carrier of claim 1, wherein an information is provided in the areaof the background layer not covered by the security element.
 13. Thedata carrier of claim 12, wherein the information is provided in form ofgaps in the background layer.
 14. The data carrier of claim 12, whereinthe information corresponds to an information on the document or thesecurity element.
 15. The data carrier of claim 12, wherein theinformation is provided in form of a code.
 16. A method for producing adata carrier of claim 1, comprising the steps of: providing the datacarrier at least in a partial area with a background layer comprising atleast one testable substance indicating authenticity of the datacarrier, and applying a security element to the background layer suchthat the security element at least partly overlaps the background layerbut does not completely cover it and the substance is still testable inthe uncovered area of the background layer.
 17. The method of claim 16,including in the applying step, applying the security element entirelywithin the area of the background layer.
 18. The method of claim 16,including forming the background layer of at least two layers, eachlayer comprising a different testable substance and applying the layersone over the other.
 19. The method of claim 16, including forming thebackground layer of at least two layers, each layer comprising adifferent testable substance and applying the layers side by side orpartly overlapping each other.
 20. The method of claim 16, comprisingapplying the background layer by printing or doctoring on the backgroundlayer.
 21. The method of claim 16, including applying the backgroundlayer by a process selected from the group consisting of screenprinting, flexography and halftone photogravure.
 22. The method of claim16, including applying the security element to the data carrier by atransfer process.
 23. The method of claim 16, including forming thesecurity element on the data carrier by applying a lacquer layer to thesurface of the data carrier, embossing the laquer layer with anembossing tool and curing the laquer layer during contact between theembossing tool and the laquer layer.
 24. The method of claim 16,including forming the security element by embossing the data carrier.25. The method of claim 16, including forming the security element byprinting an optically variable ink on the surface of the data carrier.26. A security paper with a surface, the surface being provided at leastin a partial area with a background layer comprising at least onetestable substance indicating authenticity of the security paper,wherein the surface of the security paper is provided with a securityelement and wherein the security element at least partially overlaps thebackground layer such that the background layer is not completelycovered by the security element and the substance is still testable inthe uncovered area of the background layer.